Method and apparatus for coating a plurality of cylindrical articles

ABSTRACT

An apparatus and method for simultaneously coating a plurality of cylindrical articles is disclosed. Material from a cathode is sputtered onto the articles while they are being loosely tumbled in a container surrounding the cathode.

United States Patent Salisbury et al. July 1, 1975 METHOD AND APPARATUS FOR COATING 3,818,982 6/1974 Wagner 204/298 X A PLURALITY OF CYLINDRICAL ARTICLES FOREIGN PATENTS OR APPLICATIONS 27l 92 3 I971 U... 2 4 9 [75] Inventors: Kenneth R. Salisbury, Campbell; 9 S S R 0 ,2 8

Robert J. Settzo, Painted Post, both of NY. Primary Examiner-lohn H. Mack Assisrant Examiner-D. R. Valentine [73] Asslgnee: g a Glass works Commg Attorney, Agent, or Firm-Walter S. Zebrowski;

Clarence R. Patty, Jr. [22] Filed: May 28, 1974 An apparatus and method for simultaneously coating a 35531533 plurality of cylindrical articles is disclosed. Material {58] Fieid 6 298 from a cathode is sputtered onto the articles while they are being loosely tumbled in a container sur- 56] References Cited rounding the cathode.

UNITED STATES PATENTS 15 Claims, 2 Drawing Figures 3,711,398 l/l973 Clarke 204/298 METHOD AND APPARATUS FOR COATING A PLURALITY OF CYLINDRICAL ARTICLES BACKGROUND OF THE INVENTION l. Field of the Invention The present invention relates to an apparatus and method for simultaneously coating a plurality of cylindrical articles by sputtering the coating thereon.

2. Description of the Prior Art It is known in the prior art to coat articles by various methods such as vapor deposition, sputtering, and the like. One such method is taught in the article Low Pressure Sputtering System of the Magnetron Type" by Wasa et al. in The Review of Scientific Instruments, Vol. 40, No. 5, May I969, pages 693-697. One of the principal problems in prior art methods of coating is the difficulty in applying uniform coatings, particularly for an application such as low value metal film resistors wherein a small variation in the film thickness or film property can significantly alter the resistor parameters. Furthermore, prior art methods require that the substrates to be coated are mounted or somehow fixedly placed. In addition, prior art methods and apparatus did not permit the simultaneous sputter coating of large quantities of substrates at one time. Accordingly, by the prior art methods, the cost of manufacturing such components is greatly increased as a result of the necessity of handling only a few components at a time, mounting such components, obtaining a relatively low yield of components having the desired values due to film variation, and the like.

SUMMARY OF THE INVENTION The objects of this invention are to provide a method and apparatus for simultaneously coating a plurality of cylindrical articles which permit the simultaneous coating of a large number of articles, provide uniform coating parameters, do not require the mounting of the articles, are economical, and overcome the heretofore noted disadvantages.

Broadly, according to the present invention, a method and apparatus for simultaneously coating a plu rality of cylindrical articles is provided. A plurality of cylindrical articles are placed in a rotatable container disposed within a housing. A conductive cathode having a layer of sputtering material applied to the surface thereof is disposed within the container. The container and housing is evacuated and thereafter a quantity of inert ionizable gas is introduced into the container and housing. A magnetic field is provided within the housing and the container is rotated causing the articles to tumble therein. An electrical potential is applied between the container and the cathode and the sputtering material from the cathode is sputtered onto the surfaces of the articles.

The cathode may be cooled during operation, and the articles may be preheated before sputtering if desired. In addition, a means for introducing the articles to be coated into the container is provided.

Additional objects, features, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and the attached drawings on which, by way of example, only the preferred embodiments of the present invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view, partly schematic, of the apparatus of the present invention,

FIG. 2 is a cross-sectional view of the cathode and anode of the apparatus of the present invention.

DETAILED DESCRIPTION It is to be noted that the drawings are illustrative and symbolic of the invention, and there is no intention to indicate scale or relative proportion of the elements shown therein. For purposes of simplicity, the present invention will be described in connection with the application of a resistive coating to a plurality of resistor substrates, however, the present invention is in no way limited to such an application.

Referring to FIG. 1, there is shown a housing I0 within which an article container 12 is disposed. Container 12 is mounted on shaft 14 which is ultimately driven by motor 16 through a driving means such as belt I8. Shaft 14 is mounted for rotation within bushing 20 in housing cover 22. Container 12 is preferably formed of a perforated material such as stainless steel, or the like and is open at one end. At the other end of container 12, a temporary article storage compartment 23 may be formed for purposes hereinafter described.

Referring additionally to FIG. 2, it is seen that cathode 24 is inserted into container 12 through the open end thereof. A coating 26 of sputtering material is first applied to the exterior surface of cathode 24 along the portion thereof that is intended to be within container 12. Such coating may be applied by any suitable means known in the art such as, for example, powder feed plasma spray, wire feed flame spray. or the like. Cathode 24 is fixedly mounted to housing 10 by means of flanges 28 and 30, which flanges also seai the opening in housing 10 through which cathode Z4 is disposed. It is noted that flange 30 should preferably be made of dielectric material such as glass, to facilitate electrical isolation of the cathode.

A sleeve 32 is disposed over that portion of cathode 24 within housing 10 which is not usable or suitable for sputtering. For the same reason, a cover 34 is placed over the end of cathode 24. Such sputtering shields as sleeve 32 and cover 34 may be made of any suitable nonmetallic material known in the art, such as alumina or the like.

A means is provided for introducing an inert ionizable gas into the housing and this is illustrated by means of pipe 36 and valve 38. Pipe 36 may be connected to a suitable source, not shown, of an inert ionizable gas.

For the purposes of providing a magnetic field within housing 10 and container I2, a pair of magnet coils 40 and 42. are disposed about housing 10 and connected to a suitable source of electrical energy. When it is desired to preheat the articles to be coated, a heater 44 is provided within the housing. Such a heater may be a chromalox heater or quartz-iodine lamps, or the like.

The housing is connected to a suitable vacuum source such as a diffusion pump, or the like, through opening 46. Any vacuum source which will produce a suitable vacuum is usable in connection with the present apparatus. The vacuum source is not shown.

A dc power source 48 is connected to cathode 24 and to ground. Container 12 is also grounded; such grounding being illustrated in FIG. 1 through shaft 14. As will be understood, cathode 24 must be insulated from container 12 for proper operation of the apparatus. This may be accomplished in any desired manner. If housing 10 is formed of a dielectric material, such insulation is facilitated.

As will also be understood, during application of 5 sputtering material 26 to cathode 24 as well as during sputtering itself, cathode 24 may be greatly heated, therefore, it may be necessary or desirable to cool cathode 24. Accordingly, a coolant inlet 50 and coolant outlet 52 are provided by means of which a coolant may be circulated through cathode 24. Such a coolant may be water which is circulated from inlet 50 to outlet 52. it is to be noted that electrically insulated water lines are required.

As a typical example of the present invention, a perforated stainless steel container with a temporary article storage compartment was formed and attached to a suitable drive motor for rotation within a borosilicate glass housing. A cathode was prepared from a one inch diameter copper pipe with a copper plug being silver soldered thereto at one end and water connections at the other end. A cathode coating or sputtering material was applied to the surface of said pipe by means of a powder feed plasma spray. A coating of 55% copper and 45% nickel was applied by the plasma spray to a thickness of approximately 0.1 inch. The cathode was then fixedly mounted to a flange assembly and an alumina tubing was placed over one portion of the cathode length while an alumina cap was placed over the closed end of the cathode. The portion of the cathode which was left exposed was that portion which was inserted within the container and from which sputtering is desired to take place.

A pair of magnet coils was then disposed around the housing. Each coil comprised 500 turns of number 16 enameled wire. The dc power supply connected to these coils was capable of supplying l2 amperes through the coils in parallel. Such coils will produce a magnetic field that will increase ionization sufficiently for sputtering to take place at argon pressures of as low as 5 X l0 Torr. Care was taken that no magnetic materials were used in the chamber or near the area between the coils to avoid magnetic field distortion.

A quantity of 2000 glass resistor blanks were placed in the chamber at the closed end of the container. The cathode assembly was then inserted into the open end of the container and its flange assembly was fixedly attached to the housing. The exposed portion of the cathode was disposed within the container. The cathode was then connected to a dc power supply having a current capability of 750 milliamps continuous duty and a maximum of 2500 volts. The container or anode was connected to ground. The housing was then evacuated to a vacuum of at least l0 Torr by means of a diffu sion pump connected to the housing. Argon gas was then admitted to the housing until a pressure of l X l0 Torr was reached within the housing. A magnetic field was then established within the housing by means of the magnet coils by connecting the coils to the coil power source of 32 volts. The sputtering voltage was adjusted so that the desired sputtering current of 600 ma. was obtained, and water was circulated through the cathode as a coolant therefor.

The cathode surface was then cleaned by permitting the sputtering material to be sputtered for about 10 minutes under these conditions. Such sputtering during cleaning adheres the sputtered material to the container surfaces since the resistor blanks are in the temporary article storage compartment. After cleaning, the container rotation was started which emptied the resistor blanks from the storage compartment at the end of the container into the container proper. The container rotation was adusted for approximately 5 revolutions per minute. Sputtering was then continued for a period of 30 minutes during which time material was sputtered from the cathode to the resistor blank surfaces by means of the ionized argon gas. After 30 minutes the sputtering was stopped by disconnecting the sputtering voltage and the magnetic field, as well as stopping the container rotation. The housing was then again evacuated to a pressure of approximately l0' Torr. The resistor blanks were then permitted to cool for 15 minutes after which the housing was vented to ambient, the coolant water was stopped, and the container with the resistor blanks was removed.

It was found that a coating of 55 percent copper and 45 percent nickel was applied uniformly to a thickness of 0.3 microns on all of the resistor blanks.

The resistor blanks formed by the above method and apparatus produced resistors having a resistance of l ohm/square. Depending on the results desired, the yield by this method may be up to percent.

It has been found that many other materials such, for example, as chromium, nichrome, and the like can be sputtered by the method and apparatus of the present invention. it has also been found that up to 6000 articles can be coated simultaneously by the apparatus described in the typical example, although much larger quantities are possible if the physical size of the apparatus is increased. As will be understood, the numerous variables involved in the present method such as voltages, currents, pressures, temperatures, magnetic fields, and the like will vary depending on the materials to be sputtered as well as the substrate materials and their size, and such variables must be adjusted accordingly. One skilled in the art can readily make such adjustments.

Although the present invention has been described with respect to details of certain embodiments thereof, it is not intended that such details be limitations upon the scope of the invention except insofar as set forth in the following claims.

We claim:

1. A method of simultaneously coating a plurality of cylindrical articles comprising the steps of providing a plurality of cylindrical articles,

providing an electrically conductive rotatable container within a housing,

disposing said articles in said rotatable container disposing a conductive cathode within said container,

said cathode having a layer of sputtering material on the surface thereof,

evacuating said container and housing,

introducing a quantity of inert ionizable gas into said container and housing,

rotating said container about said cathode so that said articles are caused to tumble within said container,

applying an electrical potential between said cathode and said container, and

sputtering said sputtering material from said cathode to the surface of said articles.

2. The method of claim 1 further comprising the step of forming a magnetic field within said housing and container.

3. The method of claim 1 further comprising the step of disposing said articles in a temporary storage compartment in said rotatable container, said articles entering said container when rotation thereof has begun.

4. The method of claim 3 further comprising the step of sputtering some of said sputtering material from said cathode to said container prior to rotating said container.

5. The method of claim I further comprising the step of heating said articles prior to rotating said container.

6. The method of claim 1 further comprising the step of cooling said cathode during said sputtering.

7. The method of claim 1 wherein said cylindrical articles are formed of glass.

8. The method of claim 1 wherein said inert ionizable gas is argon.

9. A tumble sputtering apparatus comprising a housing,

a rotatable electrically conductive container disposed within said housing,

means for evacuating said housing and container,

means for introducing an ionizable gas into said housing,

a conductive cathode disposed within said rotatable container,

a layer of sputtering material applied to said conductive cathode.

means for providing a magnetic field within said housing,

means for rotating said container within said housing substantially horizontally, and

means for providing an electrical potential between said cathode and said container.

10. The apparatus of claim 9 further comprising a temporary storage compartment within said container.

11. The apparatus of claim 9 further comprising means for cooling said conductive cathode.

12. The apparatus of claim 9 further comprising means for heating disposed within said housing.

13. The apparatus of claim 9 further comprising a nonmetallic shield disposed over said conductive cathode over a portion of its length within said housing extending beyond the tumbling portion of said container.

14. The apparatus of claim 9 further comprising a nonmetallic shield disposed over the end of said conductive cathode within said container.

15. The apparatus of claim 9 wherein said housing is formed of dielectric material.

II I i i 

1. A METHOD OF SIMULTANEOUSLY COATING A PLURALITY OF CYLINDRICAL ARTICLES COMPRISING THE STEPS OF PROVIDING A PLYRALITY O CYLINDIRCAL ARTICLES, PROVIDING AN ELECTRICALLY CONDCTIVE ROTATABLE CONTANER WITHIN A HOUSING, DISPOSING SAID ARTICLES IN SAID ROTATABLE CONTAINER, DISPOSING A CONDUCTIVE CATHODE WITHIN SAID CONTAINER, SAID CATHODE HAVING A LAYER OF SPUTTERING MATERIAL ON THE SURFACE THEREOF, EVACUATING SAID CONTAINER AND HOUSING, INTRODUCING A QUANTITY OF INERT IONIZABLE GAS INTO SAID CONTAINER AND HOUSING, ROTATING SAID CONTAINER ABOUT SAID CATHODE SO THAT SAID ARTICLES ARE CAUSED TO TUMBLE WITHIN SAID CONTAINER, APPLYING AN ELECTRICAL POTENTIAL BETWEEN SAID CATHODE AND SAID CONTAINER, AND SPUTTERING SAID SPUTTERING MATERIAL FROM SAID CATHODE TO THE SURFACE OF SAID ARTICLES.
 2. The method of claim 1 further comprising the step of forming a magnetic field within said housing and container.
 3. The method of claim 1 further comprising the step of disposing said articles in a temporary storage compartment in said rotatable container, said articles entering said container when rotation thereof has begun.
 4. The method of claim 3 further comprising the step of sputtering some of said sputtering material from said cathode to said container prior to rotating said container.
 5. The method of claim 1 further comprising the step of heating said articles prior to rotating said container.
 6. The method of claim 1 further comprising the step of cooling said cathode during said sputtering.
 7. The method of claim 1 wherein said cylindrical articles are formed of glass.
 8. The method of claim 1 wherein said inert ionizable gas is argon.
 9. A tumble sputtering apparatus comprising a housing, a rotatable electrically conductive container disposed within said housing, means for evacuating said housing and container, means for introducing an ionizable gas into said housing, a conductive cathode disposed within said rotatable container, a layer of sputtering material applied to said conductive cathode, means for providing a magnetic field within said housing, means for rotating said container within said housing substantially horizontally, and means for providing an electrical potential between said cathode and said container.
 10. The apparatus of claim 9 further comprising a temporary storage compartment within said container.
 11. The apparatus of claim 9 further comprising means for cooling said conductive cathode.
 12. The apparatus of claim 9 further comprisinG means for heating disposed within said housing.
 13. The apparatus of claim 9 further comprising a nonmetallic shield disposed over said conductive cathode over a portion of its length within said housing extending beyond the tumbling portion of said container.
 14. The apparatus of claim 9 further comprising a nonmetallic shield disposed over the end of said conductive cathode within said container.
 15. The apparatus of claim 9 wherein said housing is formed of dielectric material. 